Fix broken link and text

Author: rene-demonsters

src/content/docs/back-end/express-js.mdx

@@ -45,7 +45,7 @@ execute the following steps manually.
     }))
     ```
     {/* Add step about env file */}
-   _For more information on how to obtain a token, please refer to the [obtaining a token](/usage/obtaining-token) guide._
+   _For more information on how to obtain an API key, please refer to the [obtaining an API key](/usage/obtaining-api-key) guide._
 3. Modfiy the `app.js` / `app.tsx` of your React application to provide the Stringtale Context to your application.
     ```tsx
     import { StringtaleProvider } from "@stringtale/react"